Glass Cracks Below Tourists in Chicago Skydeck

In what could have been a nightmare come true, part of the glass floor in a viewing box high above Chicago cracked right below a group of California tourists. [...]

Alejandro Garibay and his family were taking in the sights at Chicago's Willis Tower on Wednesday night. The tower's Skydeck, which opened in 2009, is on the 103rd floor, about 1,353 feet above Chicago's downtown. [...]

I'm with EKE. Glass floors are on a fundamental level not smart. Glass doesn't want to resist forces perpendicular to its face. The gymnastics of laminating and etc. are attempts to make a material do what it fundamentally sucks at. Why bother?

Laminated safety glass in cars, yes. Very smart. using it as a floor is unecessary hubris. I'm not saying I want *anyone* to ever die from doing a tourist activity, but I feel the same way about people who bungee jump: if you die doing some obviously dangerous thrill-seeking activity, well...

donna - i'm taking my family up to chicago next month and literally, about a week ago, convinced my 10yo that we need to go stand on that thing (mostly as a 'conquer your fears' kind of thing for him). let's just say... i'm reconsidering...

Don't do it, Gregory, don't do it!! Honestly in my recollection the view of the skyline and lake from up there is overwhelming and terrifying (but cool) anyway, so if the 10yo is afraid of heights the main sky lobby may be enough...

Yeah, Miles, I think Louis CK is one of the most brilliant social critics of our time.

I went to a tour at Saint Gobain glass manufacturers , they make a similar product to the one of DuPont.

My understanding is that laminated glass is layered with sheets of adhesive coating between the layers. If the top layer fails this does therefore not mean that the structural integrity of the assembly is lost. The statement that fundamentally glass is better at taking compression is overly simplistic, this is an assembly.

It would be interesting to get a response from the manufacturer, which would help to clarify these differences.

Thomas, I hear your argument, but on a theoretical level I disagree, and it leads to a possible discussion of theory.

When it comes to material usage I'm an adherent of Kahn's "What does the brick want to be" school of thought. The essential quality of glass is transparency: this is what it's good at, so why are we forcing it to be structural? In the same vein, I'm not a fan of plain glass guardrails or structural glass fins. In my opinion both of those systems *look* Modern but aren't; a truly Modern attitude would appreciate the steel for its ability to support and the glass for its ability to enclose. Let the things be what they are.

You guys are silly. The cracked glass was the superficial surface layer, designed to be sacrificial. The real structural components are in the sandwich below.

C'mon everyone, this is the last thing I would expect to hear in an architect's forum! Yes, all materials have their most consonant use application - but that doesn't mean they can't be used unconventionally, when designed properly - and in fact sometimes the most unconventional uses can be the most compelling. As is the case here, in my opinion. The fact that the use of the glass is counterintuitive is precisely where the power of the design lies!

Also, we all know that basically anything can be engineered to stand up if you have enough time and money. It's not like it's utterly impossible to make a glass floor.

The college I attended for architecture school has a grand stair in the library with glass treads. Rumor has it that when originally installed they were transparent, but the college had to have them frosted because too many people were sitting under them and looking up!

Donna, I love Kahn, and even though I rate him highly as a theorist I don't think the whole honesty of material argument is particularly useful since the advent of industrial building technology. When we take the example of the brick, for example, there are a string of German and Dutch Expressionist masonry buildings which would have to be dismissed because they use brick as cladding on the ceiling. These buildings have a lovely 'brickiness' but the ceiling is counter-intuitive. I don't see anything wrong here. Similarly, I think there is nothing wrong with glass being pushed as a material in skyscrapers. I would think that Mies (judging from the sketches made for the Friedrichstrasse skyscraper in Berlin 1922) would do similar things if still alive. (although I guess he would stay clear of tacking exhibitionist glass boxes onto towers)

I have problems with terms like 'counterintuitive'. Who is the judge of this? Will you not stop development in its tracks with such an attitude? And... Can you commune with glass and ask whether or not it thinks that lamination is appropriate? Is making glass from sand not 'counter-intuitive' to begin with? Perhaps the sand is fine being sand and bumming around on the beach, who knows. Joking aside, unfortunately this is the ultimate consequence of Kahn's suggestion when he proposes that one needs to ask 'what the brick wants to be'. It seems an intellectual dead-end to me, where you cannot even use reinforced concrete.

With more traditional building materials the honesty of application is fairly unambiguous, you just use it the way it always has been used. Although even this is not as clear cut as it seems. When masonry houses started to replace timber frame in Europe people would use the brick as infill because that was what they were used to. They only later moved to load bearing walls in masonry. Currently we mostly use brick as cladding. (because we are used to the solidity of 'real' walls). Uses evolve.

Only using materials in a traditional sense will never answer current issues as how to make 'honest' and attractive details with thermal insulation and cladding systems.

I am not saying that I have figured out what a contemporary buildings should look like, but I do feel that a lot of the theories we learn in school are up for revision and are not particularly useful when you want to make a building fit for this and the next century.

Excellent post, Thomas, thank you for taking time to write it. I agree with you on many levels. I also hold certain very high theoretical ideals that I always use when considering projects, even as I know that many other ideals and forces - client desires, context, budget - will all come into play when I actually practice. I'm not an absolutist.

It's not AT ALL, for me, about using materials "traditionally". As you say, traditions change; at this point in American history staple-gunning plastic stationary shutters on either side of a window is a great builder tradition! It's about looking at the strengths and weaknesses of materials and using them appropriately, what I would consider smartly.

By the way, in my mind reinforced concrete is lovely, and smart, because you're asking the steel to act in tension and the concrete in compression (at the majority level, that is - when considering every square inch of both materials some parts of the steel are acting in compression and some of the concrete is in tension - but the majority of what you're relying on for structure is the opposite). The two materials are very good at acting in those ways, so much so that the tendency to rust when water hits steel is less significant.

IMO a significant and valid critique of, for example, OMA's CCTV building is that to make those odd shapes creates bizarre force paths that lead to excessive amounts of steel being required to make the structure work - isn't CCTV something like 3x the steel required than for a more traditional shape of the same volume? I find it hard, in our current era, to justify the Venustas leg of the stool so much more highly than the Utilitas leg.

Hm, where do glass-floored boxes hanging like leeches off the side of an otherwise expressive tower fall in the Firmitas-Utilitas-Venustas Venn diagram?! Or does Circus trump them all?

Unconventional use of materials can allow one to achieve things that are not otherwise possible. But questions remain: is that use sympathetic to the nature of the material, and will it perform economically and reliably over a specified period of time? Many products are designed for early obsolescence / failure / replacement. Many are inadvertently designed, constructed or used in ways that make them inherently dangerous.

Many people don't like being "first adopters" of new technology because they are in effect paying for the opportunity to be guinea pigs.

Novelty value is not a good reason to design and build something. Every buildings doesn't have to be a tourist attraction. Good design sets a high bar for real world performance and sustainability.

It is contrary to the nature of the material, which is what makes it so unusual - and controversial. The 'sacrificial' layer shows just how delicate it is. This was clearly fabricated in a highly controlled environment. I wonder how the repair will be done?

I prefer the floor to ceiling glass in the top level of the Hancock Tower. I find the elevated view of distant horizons preferable to the vertigo inducing view of how far I could fall.